Few details accompany the video, whose visuals and action-oriented gameplay are very Western-oriented, to say the least. The video's action sequences are broken up by concept art from GRIN that we've seen before. The only detail recognizably familiar to me, and I'm no Final Fantasy expert, is the chocobo around 1:20.

An anonymous tipster attended GRIN's going-out-of-business sale at the closed studio's…
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The host of this video (whose YouTube profile, by the way, identifies him as "William Mark Felt"), says the game is "set some time after the events of Final Fantasy XII: Revenant Wings," and is meant for the PlayStation 3, Xbox 360 and PC. "The project has not been officially announced yet, but its existence is known due to information leaked by former members of the development team and sources in the video game industry," the host said.

"The Fortress project is still supported by Square Enix and in development at a currently undisclosed studio - possibly Eidos Montreal, Square Enix's main Western branch," he said. No sources for that information were cited, although earlier reports said the project was still in development.